Ever increasing competition in cost effective semiconductor fabrication results in a continuous demand for more compact and versatile fabrication devices. A significant step during semiconductor fabrication is the repeated inspection of the wafer surfaces during intermediate fabrication of semiconductor features as are well known in the art. For that purpose, wafers need to be inspected with high throughput rates. In the prior art, a number of wafer testing devices are provided with differing complexity and space consumption to provide more or less automated wafer inspection. Wafer testing devices need to operate within expensive laboratory space. One aspect of cost efficient wafer testing is the minimum required footprint of a wafer testing device. As result, compact wafer testing devices with a footprint of less than 3 by 3 feet have been introduced in the prior art. The downside of compact wafer testing devices may be reduced through put due to separate well known wafer pre alignment and/or eventual additional need for external robotic devices for wafer transfer between a chuck at which the wafer is fixed for inspection and a cassette where a number of wafers are stacked for transport between fabrication stages. Therefore, there exists a need for a compact wafer testing device without need for pre alignment outside the device's main footprint and integrated cassette-chuck transfer. The present invention addresses this need.
At the time of this invention, wafers for semiconductor fabrication are utilized in 150 mm, 200 mm and 300 mm diameters. Therefore and to maximize the functionality of a compact wafer testing device, there exists a need for a compact wafer testing device capable of testing wafers of multiple diameters with minimum modifications. The present invention addresses this need.
There are a number of wafer cassette systems including cassette elevators commercially available that are optimized for different size wafers and other fabrication particularities as are well known to anyone skilled in the art. Therefore, there exists a need for of compact wafer testing device that provides an interface for integrating one or more freely selectable commercial cassette elevators and respective cassette systems. The present invention addresses also this need.